Siloxy porpyhrins and metal complexes thereof

ABSTRACT

The present invention involves an artificial nose having an array comprising at least a first dye and a second dye in combination and having a distinct spectral response to an analyte. In one embodiment, the first and second dyes are from the group comprising porphyrin, chlorin, chlorophyll, phthalocyanine, or salen. In a further embodiment, the first and second dyes are metalloporphyrins. The present invention is particularly useful in detecting metal ligating vapors. Further, the array of the present invention can be connected to a wavelength sensitive light detecting device.

CONTINUING APPLICATION DATA

[0001] This application is a divisional of U.S. application Ser. No.09/705,329, filed on Nov. 3, 2000, which is a Continuation-in-Part ofU.S. application Ser. No. 09/532,125, filed on Mar. 21, 2000, now U.S.Pat. No. 6,638,558.

[0002] This invention was made with Government support under ContractNos. HL25934 awarded by the National Institutes of Health & Contract No.DAAG55-97-1-2211 awarded by the Department of the Army. The Governmenthas certain rights in the invention.

FIELD OF THE INVENTION

[0003] The present invention relates to methods and apparatus forartificial olfaction, e.g., artificial noses, for the detection ofodorants by a visual display.

BACKGROUND OF THE INVENTION

[0004] There is a great need for olfactory or vapor-selective detectors(i.e., “artificial noses”) in a wide variety of applications. Forexample, there is a need for artificial noses that can detect low levelsof odorants and/or where odorants may be harmful to humans, animals orplants. Artificial noses that can detect many different chemicals aredesirable for personal dosimeters in order to detect the type and amountof odorants exposed to a human, the presence of chemical poisons ortoxins, the spoilage in foods, the presence of flavorings, or thepresence of vapor emitting items, such as plant materials, fruits andvegetables, e.g., at customs portals.

[0005] Conventional artificial noses have severe limitations anddisadvantages and are not considered generally useful for such purposes.Limitations and disadvantages of conventional artificial noses includetheir need for extensive signal transduction hardware, and theirinability to selectively target metal-coordinating vapors and toxins. Inaddition, artificial noses which incorporate mass sensitive signaltransduction or polar polymers as sensor elements are susceptible tointerference by water vapor. This limitation is significant in that itcan cause variable response of the detector with changes ambienthumidity. See F. L. Dickert, O. Hayden, Zenkel, M. E. Anal. Chem. 71,1338 (1999).

[0006] Initial work in the field of artificial noses was conducted byWilkens and Hatman in 1964, though the bulk of research done in thisarea has been carried out since the early 1980's. See, e.g., W. F.Wilkens, A. D. Hatman. Ann. NY Acad. Sci., 116, 608 (1964); K. Pursaud,G. H. Dodd. Nature, 299, 352-355 (1982); and J. W. Gardner, P. N.Bartlett. Sensors and Actuators B, 18-19, 211-220 (1994).

[0007] Vapor-selective detectors or “artificial noses” are typicallybased upon the production of an interpretable signal or display uponexposure to a vapor emitting substance or odorant (hereinafter sometimesreferred to as an “analyte”). More specifically, typical artificialnoses are based upon selective chemical binding or an interface betweena detecting compound of the artificial nose and an analyte or odorant,and then transforming that chemical binding into a signal or display,i.e., signal transduction.

[0008] Polymer arrays having a single dye have been used for artificialnoses. That is, a series of chemically-diverse polymers or polymerblends are chosen so that their composite response distinguishes a givenodorant or analyte from others. Examples of polymer array vapordetectors, including conductive polymer and conductive polymer/carbonblack composites, are discussed in: M. S. Freund, N. S. Lewis, Proc.Natl. Acad. Sci. USA 92,2652-2656 (1995); B. J. Doleman, R. D. Sanner,E. J. Severin, R. H. Grubbs, N. S. Lewis, Anal. Chem. 70, 2560-2564(1998); T. A. Dickinson, J. White, J. S. Kauer, D. R. Walt, Nature 382,697-700 (1996)(polymer array with optical detection); A. E. Hoyt, A. J.Ricco, H. C. Yang, R. M. Crooks, J. Am. Chem. Soc. 117, 8672 (1995); andJ. W. Grate, M. H. Abraham, Sensors and Actuators B 3, 85-111 (1991).

[0009] Other interface materials include functionalized self-assembledmonolayers (SAM), metal oxides, and dendrimers. Signal transduction iscommonly achieved with mass sensitive piezoelectric substrates, surfaceacoustic wave (SAW) transducers, or conductive materials. Opticaltransducers (based on absorbance or luminescence) have also beenexamined. Examples of metal oxide, SAM, and dendrimer-based detectorsare discussed in J. W. Gardner, H. V. Shurmer, P. Corcoran, Sensors andActuators B 4, 117-121 (1991); J. W. Gardner, H. V. Shurmer, T. T. Tan,Sensors and Actuators B 6, 71-75 (1992); and R. M. Crooks, A. J. Ricco,Acc. Chem. Res. 31, 219-227 (1998). These devices also use a single dye.

[0010] Techniques have also been developed using a metalloporphyrin foroptical detection of a specific, single gas such as oxygen or ammonia,and for vapor detection by chemically interactive layers on quartzcrystal microbalances. See A. E. Baron, J. D. S. Danielson, M.Gouterman, J. R. Wan, J. B. Callis, Rev. Sci. Instrum. 64, 3394-3402(1993); J. Kavandi, et al., Rev. Sci. Instrum. 61, 3340-3347 (1990); W.Lee, et al., J. Mater. Chem. 3, 1031-1035 (1993); A. A. Vaughan, M. G.Baron, R. Narayanaswamy, Anal Comm. 33,393-396 (1996); J. A. J. Brunink,et al., Anal. Chim. Acta 325,53-64 (1996); C. Di Natale, et al., Sensorsand Actuators B 44, 521-526 (1997); and C. Di Natale, et al., Mat. Sci.Eng. C 5, 209-215 (1998). However, these techniques either requireextensive signal transduction hardware, or, as noted above, are limitedto the detection of a specific, single gas. They are also subject towater vapor interference problems, as discussed previously.

[0011] While typical systems to date have demonstrated some success inchemical vapor detection and differentiation, these systems have focusedon the detection of non-metal binding or non-metal ligating solventvapors, such as arenes, halocarbons and ketones. Detection ofmetal-ligating vapors (such as amines, thiols, and phosphines) has beenmuch less explored. Further, while some single porphyrin based sensorshave been used for detection of a single strong acid, there is a needfor sensor devices that will detect a wide variety of vapors.

[0012] To summarize, there are a number of limitations and drawbacks totypical artificial noses and single porphyrin based sensors. As notedabove typical artificial noses are not designed for metal binding andmetal ligating vapors, such as amines, thiols, and phosphines. Further,typical artificial noses require extensive signal transduction hardware,and are subject to interference from water vapor. As noted above, singleporphyrin based sensors have been used for detection of a single strongacid, but cannot detect a wide variety of vapors. Thus, there is a needfor new artificial noses and methods that overcome these and otherlimitations of prior artificial noses and single porphyrin based sensorsand methods.

SUMMARY OF THE INVENTION

[0013] The present invention comprises an array of dyes including atleast a first dye and a second dye which in combination provide aspectral response distinct to an analyte or odorant. The dyes of thepresent invention produce a response in the spectrum range of about 200nanometers to 2,000 nanometers, which includes the visible spectrum oflight. It has now been discovered that an array of two or more dyesresponds to a given ligating species with a unique color patternspectrally and in a time dependent manner. Thus, dyes in the array ofthe present invention are capable of changing color in a distinct mannerwhen exposed to any one analyte or odorant. The pattern of colorsmanifested by the multiple dyes is indicative of a specific or givenanalyte. In other words, the pattern of dye colors observed isindicative of a particular vapor or liquid species.

[0014] In a preferred embodiment, the dyes of the array are porphyrinsIn another preferred embodiment, the porphyrin dyes aremetalloporphyrins. In a further preferred embodiment, the array willcomprise ten to fifty distinct metalloporphyrins in combination.Metalloporphyrins are preferable dyes in the present invention becausethey can coordinate metal-ligating vapors through open axialcoordination sites, and they produce large spectral shifts upon bindingof or interaction with metal-ligating vapors. In addition, porphyrins,metalloporphyrins, and many dyes show significant color changes uponchanges in the polarity of their environment; this so-calledsolvatochromic effect will give net color changes even in the absence ofdirect bonding between the vapor molecules and the metal ions. Thus,metalloporphyrins produce intense and distinctive changes in colorationupon ligand binding with metal ligating vapors.

[0015] The present invention provides a means for the detection ordifferentiation and quantitative measurement of a wide range of ligandvapors, such as amines, alcohols, and thiols. Further, the color dataobtained using the arrays of the present innovation may be used to givea qualitative fingerprint of an analyte, or may be quantitativelyanalyzed to allow for automated pattern recognition and/or determinationof analyte concentration. Because porphyrins also exhibit wavelength andintensity changes in their absorption bands with varying solventpolarity, weakly ligating vapors (e.g., arenes, halocarbons, or ketones)are also differentiable.

[0016] Diversity within the metalloporphyrin array may be obtained byvariation of the parent porphyrin, the porphyrin metal center, or theperipheral porphyrin substituents. The parent porphyrin is also referredto as a free base (“FB”) porphyrin, which has two central nitrogen atomsprotonated (i.e., hydrogen cations bonded to two of the central pyrrolenitrogen atoms). A preferred parent porphyrin is depicted in FIG. 2A,with the substitution of a two hydrogen ion for the metal ion (depictedas “M”) in the center of the porphyrin. In FIG. 2A, TTP stands for5,10,15,20-tetraphenylporphyrinate(-2).

[0017] In accordance with the present invention, colorimetric differencemaps can be generated by subtracting unexposed and exposedmetalloporphyrin array images (obtained, for example, with a commonflatbed scanner or inexpensive video or charge coupled device (“CCD”)detector) with image analysis software. This eliminates the need forextensive and expensive signal transduction hardware associated withprevious techniques (e.g., piezoelectric or semiconductor sensors). Bysimply differencing images of the array before and after exposure toanalytes, the present invention provides unique color change signaturesfor the analytes, for both qualitative recognition and quantitativeanalysis.

[0018] Sensor plates which incorporate vapor sensitive combinations ofdyes comprise an embodiment of the present invention which iseconomical, disposable, and can be utilized to provide qualitativeand/or quantitative identification of an analyte. In accordance with thepresent invention, a catalog of arrays and the resultant visual patternfor each analyte can be coded and placed in a look-up table or book forfuture reference. Thus, the present invention includes a method ofdetecting an analyte comprising the steps of forming an array of atleast a first dye and a second dye, subjecting the array to an analyte,inspecting the first and second dyes for a spectral response, andcomparing the spectral response with a catalog of analyte spectralresponses to identify the analyte.

[0019] Because sensing is based upon either covalent interaction (i.e.,ligation) or non-covalent solvation interactions between the analyte andthe porphyrin array, a broad spectrum of chemical species isdifferentiable. While long response times (e.g., about 45 minutes) areobserved at low analyte concentrations of about 1 ppm with large reversephase silica gel plates, use of impermeable solid supports (such aspolymer- or glass-based micro-array plates) or of small (e.g., about 1square cm.) substantially increases the low-level response to about 5minutes.

[0020] Thus, it is an object of the present invention to provide methodsand devices for artificial olfaction, vapor-selective detectors orartificial noses for a wide variety of applications. It is anotherobject of the present invention to provide methods of detection andartificial noses that can detect low levels of odorants and/or whereodorants may be harmful to living human, animal or plant cells. It isalso an object of the present invention to provide methods of olfactorydetection and artificial noses that can detect and quantify manydifferent chemicals for dosimeters that can detect chemical poisons ortoxins, that can detect spoilage in foods, that can detect flavoringsand additives, and that can detect plant materials, e.g., fruits andvegetables.

[0021] Another object of the present invention is to provide for thedetection of analytes using data analysis/pattern recognitiontechniques, including automated techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The file of this patent contains at least one drawing executed incolor. Copies of this patent with color drawing(s) will be provided bythe Patent and Trademark Office upon request and payment of thenecessary fee.

[0023]FIG. 1 illustrates an embodiment of the optical sensing plate ofthe present invention using a first elution in the y axis and a secondelution in the x axis of the plate. In this embodiment the first elutionR—OH/hexane and the second elution is R—SH/hexane.

[0024]FIG. 2A illustrates an embodiment of the invention usingmetalloporphyrins as the sensing dyes.

[0025] FIG. 2B illustrates an embodiment of the invention usingmetalloporphyrins as the sensing dyes.

[0026]FIG. 3A illustrates a vapor exposure apparatus for demonstrationof the present invention.

[0027]FIG. 3B illustrates a vapor exposure apparatus for demonstrationof the present invention.

[0028] FIG. 4 illustrates the color change profile in a metalloporphyrinarray of FIG. 2 when used in the vapor exposure apparatus of FIG. 3A todetect n-butylamine. Metalloporphyrins were immobilized on reverse phasesilica gel plates.

[0029]FIG. 5 illustrates a comparison of color changes at saturation fora wide range of analytes. Each analyte was delivered to the array as anitrogen stream saturated with the analyte vapor at 20° C. DMF standsfor dimethylformamide; THF stands for tetrahydrofuran.

[0030]FIG. 6 illustrates two component saturation responses of mixturesof 2-methylpyridine and trimethylphosphite. Vapor mixtures were obtainedby mixing two analyte-saturated N₂ streams at variable flow ratios.

[0031]FIG. 7 illustrates a comparison of Zn(TPP) spectral shifts uponexposure to ethanol and pyridine (py) in methylene chloride solution (A)and on the reverse phase support (B).

[0032]FIG. 8 illustrates another embodiment of the present invention,and more particularly, an small array comprising microwells built into awearable detector which also contains a portable light source and alight detector, such as a charge-coupled device (CCD) or photodiodearray.

[0033]FIG. 9 illustrates another embodiment of the present invention,and more particularly, a microwell porphyrin array wellplate constructedfrom polydimethylsiloxane (PDMS).

[0034]FIG. 10 illustrates another embodiment of the present invention,and more particularly, a microplate containing machined teflon posts,upon which the porphyrin array is immobilized in a polymer matrix(polystyrene/dibutylphthalate).

[0035]FIG. 11 illustrates another embodiment of the present invention,showing a microplate of the type shown in FIG. 10, consisting of aminimized array of four metalloporphyrins, showing the color profilechanges for n-octylamine, dodecanethiol, and tri-n-butylphosphine, eachat 1.8 ppm.

[0036]FIG. 12 illustrates the immunity of the present invention tointerference from water vapor.

[0037]FIG. 13 illustrates the synthesis of siloxyl-substitutedbis-pocket porphyrins in accordance with the present invention.

[0038]FIGS. 14a, 14 b, and 14 c illustrate differences in K_(eq) forvarious porphyrins.

[0039]FIG. 15 illustrates molecular models of Zn(Si₆PP) (left column)and Zn(Si₈PP) (right column).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Production of The Sensor Plate of the Present Invention A sensorplate 10 fabricated in accordance with the present invention is shown inFIG. 1. Sensor plate 10 comprises a two-dimensionally spatially resolvedarray 12 of various sensing elements or dyes 14 capable of changingcolor upon interaction (e.g., binding, pi-pi complexation, or polarityinduced shifts in color). As shown in FIG. 1, a library of such dyes 14can be given spatial resolution by two-dimensional chromatography or bydirect deposition, including, but not limited to, ink-jet printing,micropipette spotting, screen printing, or stamping. In FIG. 1,metalloporphyrin mixture 6 is placed at origin 7. Next, themetalloporphyrin mixture 6 is eluted through a silica gel orreversed-phase-silica gel 5 in sensor plate 10, and themetalloporphyrins are spatially resolved from each other and immobilizedin silica gel 5 as depicted by the oval and circular shapes 4 as shownin FIG. 1. Sensor plate 10 can be made from any suitable material ormaterials, including but not limited to, chromatography plates, paper,filter papers, porous membranes, or properly machined polymers, glasses,or metals.

[0041]FIG. 1 also illustrates an embodiment of the optical sensing plateof the present invention using a first elution 8 in the y axis and asecond elution 9 in the x axis of sensor plate 10. In this embodiment,the first elution 8 is R—OH/hexane and the second elution 9 isR—SH/hexane. The order of the first and second elutions can be reversed.The first and second elutions are used to spatially resolve themetalloporphyrin mixture 6 in silica gel 5. As shown in FIG. 1, theupper left hand quadrant 3 is characterized by metalloporphyrins thatare “hard” selective, i.e., having a metal center having a high chemicalhardness, i.e., a high charge density. As shown in FIG. 1, the lowerright hand quadrant 2 is characterized by metalloporphyrins that are“soft” selective, i.e., having a metal center having a low chemicalhardness, i.e., a low charge density. In accordance with the presentinvention, the array can be a spatially resolved collection of dyes, andmore particularly a spatially resolved combinatorial family of dyes.

[0042] In accordance with the present invention, aporphyrin-metalloporphyrin sensor plate was prepared and then used todetect various odorants. More specifically, solutions of variousmetalated tetraphenylporphyrins in either methylene chloride orchlorobenzene were spotted in 1 μL aliquots onto two carbon (“C2”, i.e,ethyl-capped) reverse phase silica thin layer chromatography plates(Product No. 4809-800, by Whatman, Inc., Clifton, N.J.) to yield thesensor array 16 seen in FIG. 2B. As shown in FIG. 2B and summarized inTable 1 below, the dyes have the following colors (the exact colorsdepend, among other things, upon scanner settings). TABLE 1 (SummarizingColors of Dyes in FIG. 2B) Sn⁴⁺—Green Co³⁺—Red Cr³⁺—Deep GreenMn³⁺—Green Fe³⁺—Dark Red Co²⁺—Red Cu²⁺—Red Ru²⁺—Light YellowZn²⁺—Greenish Red Ag²⁺—Red 2H⁺ (Free Base “FB”)—Red

[0043] A metalloporphyrin 15, sometimes referred to as M(TPP), of thepresent invention is depicted in FIG. 2A. FIG. 2A also depicts variousmetals of the metalloporphyrins 15 of the present invention, andcorresponding metal ion charge to radius ratio (i.e., Z/r Ratio) inreciprocal angstroms. The Z/r Ratio should preferably span a wide rangein order to target a wide range of metal ligating analytes. Thesemetalloporphyrins have excellent chemical stability on the solid supportand most have well-studied solution ligation chemistry. Reverse phasesilica was chosen as a non-interacting dispersion medium for themetalloporphyrin array 16 depicted in FIG. 2B, as well as a suitablesurface for diffuse reflectance spectral measurements. More importantly,the reverse phase silica presents a hydrophobic interface, whichvirtually eliminates interference from ambient water vapor. Afterspotting, sensor plates 18 like the one depicted in FIG. 2B were driedunder vacuum at 50° C. for 1 hour prior to use. Thus, immobilization ofthe metalloporphyrins on a reverse phase silica support is obtained.While ten (10) different metalloporphyrins are shown in FIG. 2A, thoseof skill in the art will recognize that many other metalloporphyrins areuseful in accordance with the present invention. Those of skill in theart will further recognize that in accordance with the broad teachingsof the present invention, any dyes capable of changing color uponinteracting with an analyte, both containing and not containing metalions, are useful in the array of the present invention.

[0044] Colorimetric Analysis Using the Sensor Plate

[0045] For the detection and analysis of odorants in accordance with thepresent invention, one needs to monitor the absorbance of the sensorplate at one or more wavelengths in a spatially resolved fashion. Thiscan be accomplished with an imaging spectrophotometer, a simple flatbedscanner (e.g. a Hewlett Packard Scanjet 3c), or an inexpensive video orCCD camera.

[0046]FIG. 3A illustrates a vapor exposure apparatus 19 of the presentinvention. FIG. 3B illustrates top and side views of bottom piece 21 anda top view of top piece 21′ of a vapor exposure flow cell 20 of thepresent invention. In an embodiment of the present invention forpurposes of demonstration, each sensor plate 18 was placed inside of astainless steel flow cell 20 equipped with a quartz window 22 as shownin FIGS. 3A and 3B. Scanning of the sensor plate 18 was done on acommercially available flatbed scanner 24 (Hewlett Packard Scanjet 3c)at 200 dpi resolution, in full color mode. Following an initial scan, acontrol run with a first pure nitrogen flow stream 26 was performed. Thearray 16 of plate 18 was then exposed to a second nitrogen flow stream28 saturated with a liquid analyte 30 of interest. As shown in FIG. 3A,the nitrogen flow stream 28 saturated with liquid analyte 30 results ina saturated vapor 32. Saturated vapor 32, containing the analyte 30 ofinterest were generated by flowing nitrogen flow stream 28 at 0.47L/min. through the neat liquid analyte 30 in a water-jacketed, glassfritted bubbler 34. Vapor pressures were controlled by regulating thebubbler 34 temperature. As shown in FIG. 3B, vapor channels 23 permitvapor flow to sensor plate 18.

EXAMPLE 1

[0047] Scanning at different time intervals and subtracting the red,green and blue (“RGB”) values of the new images from those of theoriginal scan yields a color change profile. This is shown forn-butylamine in FIG. 4, in which color change profiles of themetalloporphyrin sensor array 16 as a function of exposure time ton-butylamine vapor. Subtraction of the initial scan from a scan after 5min. of N₂ exposure was used as a control, giving a black response, asshown. 9.3% n-butylamine in N₂ was then passed over the array and scansmade after exposure for 30 s, 5 min., and 15 min. The red, green andblue (“RGB”) mode images were subtracted (absolute value) to produce thecolor change profiles illustrated. Virtually all porphyrins aresaturated after 30 seconds of exposure, yielding a color fingerprintunique for each class of analytes, which is illustrated in FIG. 4.

[0048] More specifically, subtraction of the initial scan 40 from a scanafter 5 min. of N₂ exposure was used as a control, giving a blackresponse, as shown in FIG. 4. A nitrogen flow stream containing 0.093%n-butylamine was then passed over the array 16 and scans 42, 44, and 46were made after exposure for 30 seconds, 5 minutes, and 15 minutes,respectively. The RGB mode images were subtracted (absolute value) usingAdobe Photoshop™ (which comprises standard image analyzing software),with contrast enhancement by expanding the pixel range (a 32 value rangewas expanded to 256 each for the R, G, and B values). Subtraction ofexposed and unexposed images gives color change patterns that vary inhue and intensity. Because differentiation is provided by an array ofdetectors, the system has parallels the mammalian olfactory system. Asshown in FIG. 4 and summarized in Table 2 below, the dyes have thefollowing colors in scans 42, 44, and 46. TABLE 2 (Summarizing Colors ofDyes in FIG. 4, Scans 42, 44, and 46) Sn⁴⁺—No Change Co³⁺—GreenCr³⁺—Green Mn³⁺—No Change Fe³⁺—Red Co²⁺—Faint Green Cu²⁺—No ChangeRu²⁺—No Change Zn²⁺—Light Green Ag²⁺—No Change 2H⁺(Free Base “FB”)—LightBlue

[0049] As summarized in Table 3 below, for the TTP array 16 depicted onthe left-hand side of FIG. 4, the dyes have the following colors. TABLE3 Sn⁴⁺—Greenish Co³⁺—Red Cr³⁺—Yellow with Dark Red Yellow CenterMn³⁺—Greenish Fe³⁺—Dark Red Co²⁺—Red Yellow Cu²⁺—Red Ru²⁺—Light Zn²⁺—RedYellow Ag²⁺—Red 2H⁺ (Free Base “FB”)—Red

EXAMPLE 2

[0050] Visible spectral shifts and absorption intensity differencesoccur upon ligation of the metal center, leading to readily observablecolor changes. As is well known to those with skill in the art, themagnitude of spectral shift correlates with the polarizability of theligand; hence, there exists an electronic basis for analyte distinction.Using metal centers that span a range of chemical hardness and ligandbinding affinity, a wide range of volatile analytes (including softligands, such as thiols, and harder ligands, such as amines) aredifferentiable. Because porphyrins have been shown to exhibit wavelengthand intensity changes in their absorption bands with varying solventpolarity, it is contemplated that the methods and apparatus of thepresent invention can be used to colorimetrically distinguish among aseries of weakly ligating solvent vapors (e.g., arenes, halocarbons, orketones), as shown for example in FIG. 5.

[0051] A comparison of color changes at saturation for a wide range ofanalytes is shown in FIG. 5. Each analyte is identified under thecolored array 16 that identifies each analyte.). DMF stands for theanalyte dimethylformamide, and THF stands for the analytetetrahydrofuran. As shown in FIG. 5 and summarized in Table 4 below, thecolors of each dye in response to a particular analyte are as follows.TABLE 4 Analyte: DMF Sn⁴⁺—No Change Co³⁺—Green Cr³⁺—No Change Mn³⁺—NoChange Fe³⁺—No Change Co²⁺—No Change Cu²⁺—Blue Ru²⁺—No Change Zn²⁺—NoChange Ag²⁺—No Change 2H⁺ (Free Base “FB”)—Blue Analyte: EthanolSn⁴⁺—Dark Blue Co³⁺—No Change Cr³⁺—Red Mn³⁺—No Change Fe³⁺—No ChangeCo²⁺—No Change Cu²⁺—No Change Ru²⁺—No Change Zn²⁺—Blue Ag²⁺—No Change2H⁺ (Free Base “FB”)—No Change Analyte: Pyridine Sn⁴⁺—No ChangeCo³⁺—Green Cr³⁺—Dark Green Mn³⁺—No Change Fe³⁺—No Change Co²⁺—No ChangeCu²⁺—No Change Ru²⁺—No Change Zn²⁺—Green Ag²⁺—No Change 2H⁺ (Free Base“FB”)—Blue Analyte: Hexylamine Sn⁴⁺—No Change Co³⁺—Dark Green Cr³⁺—GreenMn³⁺—No Change Fe³⁺—Red Co²⁺—No Change Cu²⁺—Blue Ru²⁺—No ChangeZn²⁺—Green Ag²⁺—Dark Blue 2H⁺ (Free Base “FB”)—Blue Analyte:Acetonitrile Sn⁴⁺—Blue Co³⁺—Dark Green Cr³⁺—No Change Mn³⁺—YellowFe³⁺—Dark Green Co²⁺—No Change Cu²⁺—Blue Ru²⁺—Blue (faint dot) Zn²⁺—BlueAg²⁺—No Change 2H⁺ (Free Base “FB”)—Blue Analyte: Acetone Sn⁴⁺—No ChangeCo³⁺—No Change Cr³⁺—Red (small dot) Mn³⁺—No Change Fe³⁺—No ChangeCo²⁺—No Change Cu²⁺—Dark Blue Ru²⁺—No Change Zn²⁺—Dark Blue Ag²⁺—NoChange 2H⁺ (Free Base “FB”)—Blue Analyte: THF Sn⁴⁺—Dark Blue Co³⁺—GreenCr³⁺—Red Mn³⁺—Blue Fe³⁺—Dark Green Co²⁺—No Change (small dot) Cu²⁺—BlueRu²⁺—No Change Zn²⁺—Blue Ag²⁺—No Change 2H⁺ (Free Base “FB”)—BlueAnalyte: CH₂ Cl₂ Sn⁴⁺—Dark Blue Co³⁺—No Change Cr³⁺—No ChangeMn³⁺—Yellow Fe³⁺—No Change Co²⁺—No Change and Red (small dot) Cu²⁺—DarkBlue Ru²⁺—No Change Zn²⁺—No Change Ag²⁺—No Change 2H⁺ (Free Base“FB”)—Blue Analyte: CHCl₃ Sn⁴⁺—Dark Blue Co³⁺—Dark Green Cr³⁺—Yellow(circle) Mn³⁺—Yellow Fe³⁺—Dark Green Co²⁺—No Change (very faint)Cu²⁺—Dark Blue Ru²⁺—No Change Zn²⁺—Blue (very faint) Ag²⁺—Blue 2H⁺ (FreeBase “FB”)—Blue (very faint) Analyte: P(OC₂ H₅ )₃ Sn⁴⁺—No ChangeCo³⁺—Yellow Cr³⁰ —Dark Green Mn³⁺—No Change Fe³⁺—Dark GreenCo²⁺—Greenish Yellow (very faint) Cu²⁺—Dark Blue (faint) Ru²⁺—No ChangeZn²⁺—Greenish Blue Ag²⁺—Blue (very faint) 2H⁺ (Free Base “FB”)—BlueAnalyte: P(C₄ H₉ )₃ Sn⁴⁺—No Change Co³⁺—Yellow and Red Cr³⁺—Deep RedMn³⁺—No Change Fe³⁺—Dark Green (faint) Co²⁺—Red (with some yellow)Cu²⁺—No Change Ru²⁺—Dark Blue Zn²⁺—Yellow Ag²⁺—No Change 2H⁺ (Free Base“FB”)—No Change Analyte: C₆ H₁₃ SH Sn⁴⁺—Green Co³⁺—No Change Cr³⁺—Yellowcircle surrounded by greenish blue circle Mn³⁺—Yellow Fe³⁺—Dark GreenCo²⁺—No Change Cu²⁺—Dark Blue (faint) Ru²⁺—No Change Zn²⁺—GreenAg²⁺—Blue (very faint) 2H⁺ (Free Base “FB”)—Blue Analyte: (C₃ H₇ )₂ SSn⁴⁺—Dark Blue (faint) Co³⁺—Deep Green Cr³⁺—Green Mn³⁺—No ChangeFe³⁺—Dark Green Co²⁺—Dark Green (very faint) Cu²⁺—Dark Blue (faint)Ru²⁺—Green Zn²⁺—Green Ag²⁺—Blue (very faint) 2H⁺ (Free Base “FB”)—BlueAnalyte: Benzene Sn⁴⁺—No Change Co³⁺—Green Cr³⁺—Yellow (very faint)Mn³⁺—Yellow (some green) Fe³⁺—Dark Green Co²⁺—No Change Cu²⁺—No ChangeRu²⁺—No Change Zn²⁺—Dark Green Ag²⁺—No Change 2H⁺ (Free Base “FB”)—Blue

[0052] The degree of ligand softness (roughly their polarizability)increases from left to right, top to bottom as shown in FIG. 1. Eachanalyte is easily distinguished from the others, and there are familyresemblances among chemically similar species (e.g., pyridine andn-hexylamine). Analyte distinction originates both in the metal-specificligation affinities and in their specific, unique color changes uponligation. Each analyte was delivered to the array as a nitrogen streamsaturated with the analyte vapor at 20° C. (to ensure completesaturation, 30 min. exposures to vapor were used. Although thesefingerprints were obtained by exposure to saturated vapors (thousands ofppm), unique patterns can be identified at much lower concentrations.

[0053] The metalloporphyrin array 16 has been used to quantify singleanalytes and to identify vapor mixtures. Because the images' colorchannel data (i.e., RGB values) vary linearly with porphyrinconcentration, we were able to quantify single porphyrin responses todifferent analytes. Color channel data were collected for individualspots and plotted, for example, as the quantity(R_(plt)−R_(spt))/(R_(plt)), (where R_(plt) was the red channel valuefor the initial silica surface and R_(spt) the average value for thespot. For example, Fe(TFPP)(Cl) responded linearly to octylamine between0 and 1.5 ppm. Other porphyrins showed linear response ranges thatvaried with ligand affinity (i.e., equilibrium constant).

EXAMPLE 3

[0054] The array of the present invention has demonstrated interpretableand reversible responses even to analyte mixtures of strong ligands,such as pyridines and phosphites, as is shown in FIG. 6. Color changepatterns for the mixtures are distinct from either of the neat vapors.Good reversibility was demonstrated for this analyte pair as the vapormixtures were cycled between the neat analyte extremes, as shown in FIG.6, which shows the two component saturation responses to mixtures of2-methylpyridine (“2MEPY”) and trimethylphosphite (“TMP”). Vapormixtures were obtained by mixing the analyte-saturated N₂ streams atvariable flow ratios. A single plate was first exposed to puretrimethylphosphite vapor in N₂ (Scan A), followed by increasing molefractions of 2-methylpyridine up to pure 2-methylpyridine vapor (ScanC), followed by decreasing mole fractions of 2-methylpyridine back topure trimethylphosphite vapor. In both directions, scans were taken atthe same mole fraction trimethylphosphite and showed excellentreversibility; scans at mole fractions at 67% trimethylphosphite(χ_(tmp)=0.67, Scans B and D) and of their difference map are shown(Scan E). Response curves for the individual porphyrins allow forquantification of the mixture composition. The colors of each dye uponexposure to the analytes TMP and 2MEPY are shown in FIG. 6 and aresummarized in Table 5 below. TABLE 5 Scan A, Analyte: Neat TMP Sn⁴⁺—DarkBlue Co³⁺—Yellow Cr³⁺—No Change Mn³⁺—Yellow with red center Fe³⁺—DarkGreen Co²⁺—Greenish Yellow Cu²⁺—Dark Blue Ru²⁺—No Change Zn²⁺—BlueAg²⁺—Green (very faint) 2H⁺ (Free Base “FB”)— Reddish Blue Scan B,Analyte: TMP,x_(TMP) = 0.67 Sn⁴⁺—Blue Co³⁺—Green Cr³⁺—Green (small dot)Mn³⁺—Yellow and Green Fe³⁺—Green and Yellow Co²⁺—Green with red centerCu²⁺—Dark Blue Ru²⁺—Purple (very faint) Zn²⁺—Blue Ag²⁺—Greenish Blue 2H⁺(Free Base “FB”)— Reddish Blue Scan C, Analyte: Neat 2MEPY Sn⁴⁺—BlueCo³⁺—Green Cr³⁺—No Change Mn³⁺—Yellow and Green with Fe³⁺—Red with someYellow Co²⁺—Green Red center Cu²⁺—Dark Blue Ru²⁺—Deep Blue Zn²⁺—Greenwith some Blue Ag²⁺—Green with some Blue 2H⁺ (Free Base “FB”)— ReddishBlue Scan D, Analyte: TMP,x_(TMP =) 0.67 Sn⁴⁺—Blue Co³⁺—Green Cr⁺—NoChange Mn³⁺—Yellow and Green Fe³⁺—Green and Yellow Co²⁺—Green Cu²⁺—DarkBlue Ru²⁺—Purple (very faint) Zn²⁺—Blue Ag²⁺—Greenish Blue (very 2H⁺(Free Base “FB”)— faint) Reddish Blue Scan E Sn⁴⁺—No Change Co³⁺—NoChange Cr³⁺—No Change Mn³⁺—No Change Fe³⁺—No Change Co²⁺—No ChangeCu²⁺—Blue (very faint) Ru²⁺—Blue (small dot) Zn²⁺—No Change Ag²⁺—Blue(very faint) 2H⁺ (Free Base “FB”)—Green

[0055] In an effort to understand the origin of the color changes uponvapor exposure, diffuse reflectance spectra were obtained for singleporphyrin spots before and after exposure to analyte vapors. Porphyrinsolutions were spotted in 50 μL aliquots onto a plate and allowed to dryunder vacuum at 50° C. Diffuse reflectance spectra of the plate werethen taken using a UV-visible spectrophotometer equipped with anintegrating sphere. Unique spectral shifts were observed upon analyteexposure, which correlated well with those seen from solution ligation.For example, Zn(TPP) exposure to ethanol and pyridine gave unique shiftswhich were very similar to those resulting from ligand exposure insolution. FIG. 7 shows a comparison of Zn(TPP) spectral shifts uponexposure to ethanol and pyridine (py) in methylene chloride solution (A)and on the reverse phase support (B). In both A and B, the bandscorrespond, from left to right, to Zn(TPP), Zn(TPP)(C₂H₅OH), andZn(TPP)(py), respectively. Solution spectra (A) were collected using aHitachi U-3300 spectrophotometer; Zn(TPP), C₂H₅OH, and py concentrationswere approximately 2 μM, 170 mM, and 200 μM, respectively. Diffusereflectance spectra (B) were obtained with an integrating sphereattachment before exposure to analytes, after exposure to ethanol vaporin N₂, and after exposure to pyridine vapor in N₂ for 30 min. each usingthe flow cell.

[0056] Improvement to Low Concentration Response

[0057] Color changes at levels as low as 460 ppb have been observed foroctylamine vapor, albeit with slow response times due to the highsurface area of the silica on the plate 18. The surface area of C2plates is ≈350 m²/gram. Removal of excess silica gel surrounding theporphyrin spots from the plate 18 led to substantial improvements inresponse time for exposures to trace levels of octylamine. Because thehigh surface area of the reverse phase silica surface is primarilyresponsible for the increased response time, other means of solidsupport or film formation can be used to improve low concentrationresponse.

[0058] Further, the present invention contemplates miniaturization ofthe array using small wells 60 (<1 mm), for example in glass, quartz, orpolymers, to hold metalloporphyrin or other dyes as thin films, whichare deposited as a solution, by liquid droplet dispersion (e.g.,airbrush or inkjet), or deposited as a solution of polymer withmetalloporphyrin.

[0059] These embodiments are depicted in FIGS. 8, 9, and 10. FIG. 8illustrates the interfacing of a microplate 60 into an assemblyconsisting of a CCD 70, a microplate 72 and a light source 74. FIG. 9illustrates another embodiment of the present invention, and moreparticularly, a microwell porphyrin array wellplate 80 constructed frompolydimethylsiloxane (PDMS). The colors of the dyes shown in FIG. 9 aresummarized below in Table 6. TABLE 6 Sn⁴⁺—Dark Red Co³⁺—Dark RedCr³⁺—Dark Green Mn³⁺—Green Fe³⁺—Dark Red Co²⁺—Yellowish Green Cu²⁺—DeepRed Ru²⁺—Dark Red Zn²⁺—Red Ag²⁺—Red 2H⁺ (Free with some Yellow Base“FB”)—Red

[0060]FIG. 10 demonstrates deposition of metalloporphyrin/polymer(polystyrene/dibutylphthalate) solutions upon a plate, which includes aseries of micro-machined Teflon® posts 100 having the same basicposition relative to each other as shown in FIG. 2A and FIG. 2B. Thecolors for the dyes in the middle of FIG. 10 are summarized in Table 7below. TABLE 7 Sn⁴⁺—Yellow Co³⁺—Orange Cr³⁺—Yellow Mn³⁺—YellowFe³⁺—Orange Co²⁺—Orange Cu²⁺—Orange Ru²⁺—Dark Yellow Zn²⁺—OrangeAg²⁺—Orange 2H⁺ (Free Base “FB”)—Red

[0061] The colors for the dyes on the right hand side of FIG. 10 aresummarized in Table 8 below. TABLE 8 Sn⁴⁺—No Change Co³⁺—Green Cr³⁺—RedMn³⁺—Blue Fe³⁺—Red Co²⁺—Red, Green, Blue, and Yellow Cu²⁺—Green withsome Ru²⁺—Blue (very faint) Zn²⁺—Yellow Blue with some Red Ag²⁺—Greenwith some 2H+ (Free Base “FB”)—Green Blue with some Blue

EXAMPLE 5

[0062]FIG. 11 shows the color profile changes from a microplate of thetype shown in FIG. 10. The microplate, consisting of a minimized arrayof four metalloporphyrins, i.e., Sn(TPP)(Cl₂), Co(TPP)(Cl), Zn(TPP),Fe(TFPP)(Cl), clockwise from the upper left (where TFPP stands for5,10,15,20-tetrakis(pentafluorophenyl)porphyrinate). The color profilechanges are shown in FIG. 11 after exposure to low levels ofn-octylamine, dodecanethiol (C₁₂H₂₅ SH), and tri-n-butylphosphine(P(C₄H₉)₃), each at 1.8 ppm, which is summarized in Table 9 below. TABLE9 Dyes on Teflon ® Sn—Dark Yellow Co—Red Zn—Red Fe—Orange with Redoutline Dyes exposed to n-octylamine Sn—No Change Co—Green (very faint)Zn—Red Fe—Green Dyes exposed to C₁₂ H₂₅ SH Zn—Red with some greenFe—Blue (very faint) and yellow Dyes exposed to P(C₄ H₉ )₃ Sn—No ChangeCo—Yellow with red center and some red periphery Zn—Green Fe—Yellow withsome Green and Blue

[0063] The low ppm levels of octylamine, an analyte of interest, weregenerated from temperature-regulated octylamine/dodecane solutions withthe assumption of solution ideality. The dodecane acts as a diluent tolower the level of octylamine vapor pressure for the purposes of thisdemonstration of the invention.

EXAMPLE 6

[0064]FIG. 12 illustrates the immunity of the present invention tointerference from water vapor. The hydrophobicity of the reverse phasesupport greatly any possible effects from varying water vapor in theatmosphere to be tested. For instance, as shown in FIG. 12, a colorfingerprint generated from exposure of the array to n-hexylamine (0.86%in N₂) was identical to that for n-hexylamine spiked heavily with watervapor (1.2% H₂O, 0.48% hexylamine in N₂). See scans 120, 122 and 124.The ability to easily detect species in the presence of a large waterbackground represents a substantial advantage over mass-sensitivesensing techniques or methodologies that employ polar polymers as partof the sensor array. The color patterns shown in FIG. 12 are summarizedin Table 10 below. TABLE 10 Scan 120 Sn⁴⁺—No Change Co³⁺—GreenCr³⁺—Green Mn³⁺—No Change Fe³⁺—Red Co²⁺—No Change Cu²⁺—No Change Ru²⁺—NoChange Zn²⁺—Green Ag²⁺—No Change 2H⁺ (Free Base “FB”)—Dark Blue Scan 122Sn⁴⁺—No Change Co³⁺—Green Cr³⁺—Green Mn³⁺—No Change Fe³⁺—Red Co²⁺—NoChange Cu²⁺—No Change Ru²⁺—Green (small dot) Zn²⁺—Green Ag²⁺—No Change2H⁺ (Free Base “FB”)—Dark Blue Scan 124 Sn⁴⁺— Co³⁺—Bluish CircleCr³⁺—Bluish Circle Bluish Circle Mn³⁺— Fe³⁺—Bluish Circle Co²⁺— BluishCircle Bluish Circle Cu²⁺— Ru²⁺—Bluish Circle Zn²⁺— Bluish Circle BluishCircle Ag²⁺— 2H⁺ (Free Base “FB”)— Bluish Circle Bluish Circle

[0065] Additional Features of the Preferred Embodiments of the Invention

[0066] Having demonstrated electronic differentiation, an importantfurther goal is the shape-selective distinction of analytes (e.g.,n-hexylamine vs. cyclohexylamine). Functionalized metalloporphyrins thatlimit steric access to the metal ion are candidates for suchdifferentiation. For instance, we have been able to control ligation ofvarious nitrogenous ligands to dendrimer-metalloporphyrins and induceselectivities over a range of more than 10⁴. As an initial attempttoward shape-selective detection, we employed the slightly-hinderedtetrakis(2,4,6-trimethoxyphenyl)porphyrins (TTMPP) in our sensing array.With these porphyrins, fingerprints for t-butylamine and n-butylamineshowed subtle distinctions, as did those for cyclohexylamine andn-hexylamine. Using more hindered metalloporphyrins, it is contemplatedthat the present invention can provide greater visual differentiation.Such porphyrins include those whose periphery is decorated withdendrimer, siloxyl, phenyl, t-butyl and other bulky substituents,providing sterically constrained pockets on at least one face (andpreferably both) of the porphyrin.

[0067] In a similar fashion, it is contemplated that the sensor platesof the present invention can be used for the detection of analytes inliquids or solutions, or solids. A device that detects an analyte in aliquid or solution or solid can be referred to as an artificial tongue.Proper choice of the metal complexes and the solid support must precludetheir dissolution into the solution to be analyzed. It is preferred thatthe surface support repel any carrier solvent to promote the detectionof trace analytes in solution; for example, for analysis of aqueoussolutions, reverse phase silica has advantages as a support since itwill not be wetted directly by water.

[0068] Alternative sensors in accordance with the present invention mayinclude any other dyes or metal complexes with intense absorbance in theultraviolet, visible, or near infrared spectra that show a color changeupon exposure to analytes. These alternative sensors include, but arenot limited to, a variety of macrocycles and non-macrocycles such aschlorins and chlorophylls, phthalocyanines and metallophthalocyanines,salen-type compounds and their metal complexes, or othermetal-containing dyes.

[0069] The present invention can be used to detect a wide variety ofanalytes regardless of physical form of the analytes. That is, thepresent invention can be used to detect any vapor emitting substance,including liquid, solid, or gaseous forms, and even when mixed withother vapor emitting substances, such solution mixtures of substances.

[0070] The present invention can be used in combinatorial libraries ofmetalloporphyrins for shape selective detection of substrates where thesubstituents on the periphery of the macrocycle or the metal bound bythe porphyrin are created and then physically dispersed in twodimensions by (partial) chromatographic or electrophoretic separation.

[0071] The present invention can be used with chiral substituents on theperiphery of the macrocycle for identification of chiral substrates,including but not limited to drugs, natural products, blood or bodilyfluid components.

[0072] The present invention can be used for analysis of biologicalentities based on the surface proteins, oligosacharides, antigens, etc.,that interact with the metalloporphyrin array sensors of the presentinvention. Further, the sensors of the present invention can be used forspecific recognition of individual species of bacteria or viruses.

[0073] The present invention can be used for analysis of nucleic acidsequences based on sequence specific the surface interactions with themetalloporphyrin array sensors. The sensors of the present invention canbe used for specific recognition of individual sequences of nucleicacids. Substituents on the porphyrins that would be particularly usefulin this regard are known DNA intercalating molecules and nucleic acidoligomers.

[0074] The present invention can be used with ordinary flat bedscanners, as well as portable miniaturized detectors, such as CCDdetectors with microarrays of dyes such as metalloporphyrins.

[0075] The present invention can be used for improved sensitivity,automation of pattern recognition of liquids and solutions, and analysisof biological and biochemical samples.

[0076] Superstructure Bonded to the Periphery of the Porphyrin

[0077] The present invention includes modified porphyrins that have asuperstructure bonded to the periphery of the porphyrin. Asuperstructure bonded to the periphery of the porphyrin in accordancewith the present invention includes any additional structural element orchemical structure built at the edge of the porphyrin and bondedthereto.

[0078] The superstructures can include any structural element orchemical structure characterized in having a certain selectivity. Thoseof skill in the art will recognize that the superstructures of thepresent invention include structures that are shape selective, polarityselective, inantio selective, regio selective, hydrogen bondingselective, and acid-base selective. These structures can includesiloxyl-substituted substituents, nonsiloxyl-substituted substituentsand nonsiloxyl-substituted substituents, including but not limited toaryl substituents, alkyl substituents, and organic, organometallic, andinorganic functional group substituents.

[0079] Superstructure Bis-Pocket Porphyrins

[0080] A number of modified porphyrins have been synthesized to mimicvarious aspects of the enzymatic functions of heme proteins, especiallyoxygen binding (myoglobin and hemoglobin) and substrate oxidation(cytochrome P-450). See Suslick, K. S.; Reinert, T. J. J. Chem. Ed.1985, 62, 974; Collman, J. P.; Zhang, X.; Lee, V. J.; Uffelman, E. S.;Brauman, J. I. Science 1993,261, 1404; Collman, J. P.; Zhang, X. inComprehensive Supramolecular Chemistry; Atwood, J. L.; Davies, J. E. D.;MacNicol, D. D.; Vogtel, F. Eds.; Pergamon: New York, 1996; vol. 5, pp.1-32; Suslick, K. S.; van Deusen-Jeffries, S. in ComprehensiveSupramolecular Chemistry; Atwood, J. L.; Davies, J. E. D.; MacNicol, D.D.; Vogtel, F. Eds.; Pergamon: New York, 1996; vol. 5, pp. 141-170;Suslick, K. S. in Activation and Functionalization of Alkanes; Hill, C.L., ed.; Wiley & Sons: New York, 1989; pp. 219-241. The notable propertyof many heme proteins is their remarkable substrate selectivity; thedevelopment of highly regioselective synthetic catalysts, however, isstill at an early stage. Discrimination of one site on a molecule fromanother and distinguishing among many similar molecules presents adifficult and important challenge to both industrial and biologicalchemistry. See Metalloporphyrins in Catalytic Oxidations; Sheldon, R. A.Ed. Marcel Dekker: New York, 1994). Although the axial ligationproperties of simple synthetic metalloporphyrins are well documented inliterature, see Bampos, N.; Marvaud, V.; Sanders, J. K. M. Chem. Eur. J.1998, 4, 325; Stibrany, R. T.; Vasudevan, J.; Knapp, S.; Potenza, J. A.;Emge, T.; Schugar, H. J. J. Am. Chem. Soc. 1996, 118, 3980, size andshape control of ligation to peripherally modified metalloporphyrins hasbeen largely unexplored, with few notable exceptions, where only limitedselectivities have been observed. See Bhyrappa, P.; Vaijayanthimala, G.;Suslick, K. S. J. Am. Chem. Soc. 1999, 121, 262; Imai, H.; Nakagawa, S.;Kyuno, E. J. Am. Chem. Soc. 1992, 114, 6719.

[0081] The present invention includes the synthesis, characterizationand remarkable shape-selective ligation of silylether-metalloporphyrinscaffolds derived from the reaction of5,10,15,20-tetrakis(2′,6′-dihydroxyphenyl)porphyrinatozinc(II) witht-butyldimethylsilyl chloride, whereby the two faces of the Zn(II)porphyrin were protected with six, seven, or eight siloxyl groups. Thisresults in a set of three porphyrins of nearly similar electronics butwith different steric encumbrance around central metal atom present inthe porphyrin. Ligation to Zn by classes of different sized ligandsreveal shape selectivities as large as 10⁷.

[0082] A family of siloxyl-substituted bis-pocket porphyrins wereprepared according to the scheme of FIG. 13. The abbreviations of theporphyrins that can be made in accordance with the scheme shown in FIG.13 are as follows:

[0083] Zn(TPP), 5,10,15,20-tetraphenylporphyrinatozinc(II);

[0084] Zn[(OH)₆PP],5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);

[0085] Zn[(OH)₈PP],5,10,15,20-tetrakis(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);

[0086] Zn(Si₆PP),5(phenyl)-10,15,20-trikis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II);

[0087] Zn(Si₇OHPP),5,10,15-trikis(2^(/),6^(/)-disilyloxyphenyl)-20-(2^(/)-hydroxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II);

[0088] Zn(Si₈PP),5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II).The synthesis of Zn[(OH)₆PP], Zn(Si₆PP), and Zn(Si₈PP) is detailedbelow. Zn[(OH)₆PP] and Zn[(OH)₈PP] were obtained (see Bhyrappa, P.;Vaijayanthimala, G.; Suslick, K. S. J. Am. Chem. Soc. 1999, 121,262)from demethylation (see Momenteau, M.; Mispelter, J.; Loock, B.;Bisagni, E. J. Chem. Soc. Perkin Trans. 1, 1983, 189) of correspondingfree base methoxy compounds followed by zinc(II) insertion. The methoxyporphyrins were synthesized by acid catalysed condensation of pyrrolewith respective benzaldehydes following Lindsey procedures. See Lindsey,J. S.; Wagner, R. W. J. Org. Chem. 1989, 54, 828. Metalation was done inmethanol with Zn(O₂CCH₃)₂. The t-butyldimethylsilyl groups wereincorporated into the metalloporphyrin by stirring a DMF solution ofhydroxyporphyrin complex with TBDMSiCl (i.e., t-butyldimethylsilylchloride) in presence of imidazole. See Corey, E. J; Venkateswarlu, A.J. Am. Chem. Soc. 1972, 94, 6190. The octa (Zn(Si₈PP)), hepta(Zn(Si₇OHPP)), and hexa (Zn(Si₆PP)) silylether porphyrins were obtainedfrom Zn[(OH)₈PP] and Zn[(OH)₆PP], respectively. The compounds werepurified by silica gel column chromatography and fully characterized byUV-Visible, ¹H-NMR, HPLC, and MALDI-TOF MS.

[0089] The size and shape selectivities of the binding sites of thesebis-pocket Zn silylether porphyrins were probed using the axial ligationof various nitrogenous bases of different shapes and sizes in toluene at25° C. Zn(II) porphyrins were chosen because, in solution, theygenerally bind only a single axial ligand. Successive addition of ligandto the porphyrin solutions caused a red-shift of the Soret band typicalof coordination to zinc porphyrin complexes. There is no evidence fromthe electronic spectra of these porphyrins for significant distortionsof the electronic structure of the porphyrin. The binding constants(K_(eq)) and binding composition (always 1:1) were evaluated usingstandard procedures. See Collman, J. P.; Brauman, J. I.; Doxsee, K. M.;Halbert, T. R.; Hayes, S. E.; Suslick, K. S. J. Am. Chem. Soc. 1978,100, 2761; Suslick, K. S.; Fox, M. M.; Reinert, T. J. Am. Chem. Soc.1984, 106,4522. The K_(eq) values of the silylether porphyrins withnitrogenous bases of different classes are compared with the stericallyundemanding Zn(TPP) in FIGS. 14a, 14 b, and 14 c. It is worth noting theparallel between shape selectivity in these equilibrium measurements andprior kinetically-controlled epoxidation and hydroxylation. See Collman,J. P.; Zhang, X. in Comprehensive Supramolecular Chemistry; Atwood, J.L.; Davies, J. E. D.; MacNicol, D. D.; Vogtel, F. Eds.; Pergamon: NewYork, 1996; vol. 5, pp. 1-32; Suslick, K. S.; van Deusen-Jeffries, S. inComprehensive Supramolecular Chemistry; Atwood, J. L.; Davies, J. E. D.;MacNicol, D. D.; Vogtel, F. Eds.; Pergamon: New York, 1996; vol. 5, pp.141-170; Suslick, K. S. in Activation and Functionalization of Alkanes;Hill, C. L., ed.; Wiley & Sons: New York, 1989; pp. 219-241; Bhyrappa,P.; Young, J. K.; Moore, J. S.; Suslick, K. S. J. Am. Chem. Soc., 1996,118, 5708-5711. Suslick, K. S.; Cook, B. R. J. Chem. Soc., Chem. Comm.1987,200-202; Cook, B. R.; Reinert, T. J.; Suslick, K. S. J. Am. Chem.Soc. 1986, 108, 7281-7286; Suslick, K. S.; Cook, B. R.; Fox, M. M. J.Chem. Soc., Chem. Commun. 1985, 580-582. The selectivity forequilibrated ligation appears to be substantially larger than forirreversible oxidations of similarly shaped substrates.

[0090] The binding constants of silylether porphyrins are remarkablysensitive to the shape and size of the substrates relative to Zn(TPP).See FIGS. 14a, 14 b, and 14 c. The binding constants of different aminescould be controlled over a range of 10¹ to 10⁷ relative to Zn(TPP). Itis believed that these selectivities originate from strong stericrepulsions created by the methyl groups of the t-butyldimethylsiloxylsubstituents. The steric congestion caused by these bulky silylethergroups is pronounced even for linear amines and small cyclic amines(e.g., azetidine and pyrrolidine).

[0091] There are very large differences in K_(eq) for porphyrins havingthree versus four silylether groups on each face (e.g., hexa- vs.octa-silylether porphyrins), as expected based on obvious stericarguments (see FIGS. 14a, 14 b, and 14 c). Even between the hexa- overhepta-silylether porphyrins, however, there are still substantialdifferences in binding behavior. It is believed that this is probablydue to doming of the macrocycle in the hexa- and hepta-silyletherporphyrins, which lessens the steric constraint relative to theoctasilylether porphyrin. Such doming will be especially important inporphyrins whose two faces are not identical. The free hydroxyfunctionality of the hepta-silylether may play a role in binding ofbi-functionalized ligands (e.g., free amino acids); for the simpleamines presented here, however, we have no evidence of any specialeffects.

[0092] These silylether porphyrins showed remarkable selectivities fornormal, linear amines over their cyclic analogues. For a series oflinear amines (n-propylamine through n-decylamine), K_(eq) were verysimilar for each of the silylether porphyrins. In comparison, therelative K_(eq) for linear versus cyclic primary amines (FIG. 14a,n-butylamine vs. cyclohexylamine) were significantly different: K_(eq)^(linear)/K_(eq) ^(cyclic) ranges from 1 to 23 to 115 to >200 forZn(TPP), Zn(Si₆PP), Zn(Si₇OHPP), and Zn(Si₈PP), respectively. Theability to discriminate between linear and cyclic compounds is thusestablished.

[0093] A series of cyclic 2° amines (FIG. 14b) demonstrate theremarkable size and shape selectivities of this family of bis-pocketporphyrins. Whereas the binding constants to Zn(TPP) with those aminesare virtually similar. In contrast, the K_(eq) values for silyletherporphyrins strongly depend on the ring size and its peripheralsubstituents. The effect of these shape-selective binding sites isclear, even for compact aromatic ligands with non-ortho methylsubstituents (FIG. 14c).

[0094] The molecular structures of these silylether porphyrins explainstheir ligation selectivity. The x-ray single crystal structure ofZn(Si₈PP) has been solved in the triclinic P1 bar space group. SeeSingle crystal x-ray structure of Zn(Si₈PP) shown in FIG. 15. As shownin FIG. 15, Zn(Si₆PP) (energy minimized molecular model) and Zn(Si₈PP)(single crystal x-ray structure) have dramatically different bindingpockets. In the octasilylether porphyrin, the top access on both facesof the porphyrin is very tightly controlled by the siloxyl pocket. Incontrast, the metal center of the hexasilylether porphyrin isconsiderably more exposed for ligation.

[0095]FIG. 15 illustrates molecular models of Zn(Si₆PP) (left column)and Zn(Si₈PP) (right column). The pairs of images from top to bottom arecylinder side-views, side-views, and top-views, respectively; spacefilling shown at 70% van der Waals radii; with the porphyrin carbonatoms shown in purple, oxygen atoms in red, silicon atoms in green, andZn in dark red. The x-ray single crystal structure of Zn(Si₈PP) isshown; for Zn(Si₆PP), an energy-minimized structure was obtained usingCerius 2 from MSI.

[0096] In summary, a series of bis-pocket siloxyl metalloporphyrincomplexes were prepared with sterically restrictive binding pockets onboth faces of the macrocycle. Ligation to Zn by various nitrogenousbases of different sizes and shapes were investigated. Shapeselectivities as large as 10⁷ were found, compared to unhinderedmetalloporphyrins. Fine-tuning of ligation properties of theseporphyrins was also possible using pockets of varying steric demands.The shape selectivities shown here rival or surpass those of anybiological system.

[0097] Examples of Synthesis of Superstructured Porphyrins andMetalloporphyrins

[0098] Synthesis of5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxy-phenyl)-porphyrinatozinc(II),Zn[(OH)₆PP]:

[0099] The free base5-phenyl-10,15,20-tris(2^(/),6^(/)-dimethoxyphenyl)-porphyrin wassynthesized by Lewis acid catalyzed condensation of2,6-dimethoxybezaldehyde and benzaldehyde with pyrrole (3:1:4 moleratio) following the Lindsey procedure. See Lindsey, J. S.; Wagner, R.W. J. Org. Chem. 1989, 54, 828. The mixture of products thus formed waspurified by silica gel column chromatography (if necessary, using CH₂Cl₂as eluant). The isolated yield of the desired product was found to be 7%(wrt pyrrole used). The corresponding hydroxyporphyrins were obtained bydemethylation with pyridine hydrochloride. See Momenteau, M.; Mispelter,J.; Loock, B.; Bisagni, E. J. Chem. Soc. Perkin Trans. 1, 1983, 189.After typical work-up known to those skilled in the art, the crudecompound was purified by silica gel column chromatography usingethylacetate as eluant. The first fraction was Zn[(OH)₆PP], which wascollected and the solvent was removed. The yield of the product was 90%(based on starting hydroxyporphryin). ¹H NMR of H₂[(OH)₆PP] inacetone-d₆ (ppm): 8.96-8.79(m, 8H, b-pyrrole H), 8.24(m, 2H, o-H5-Phenyl), 8.07 and 8.02(2s, 6H, —OH), 7.83(m, 3H, m,p-H 5-Phenyl),7.50(t, 3H, p-H hydroxyphenyl), 6.90(d, 6H, m-H hydroxyphenyl), −2.69(s,2H, imino-H). Elemental analysis, calcd. for C₄₄H₃₀O₆N₄.H₂O: C=72.5,H=4.4 and N=7.7%. Found C=72.7, H=4.4 and N=7.4%. The compound showedmolecular ion peak at 711 (m/z calcd. for C₄₄H₃₀O₆N₄=710) in FAB-MS.

[0100] The Zn derivative was obtain by stirring methanol solution ofH₂[(OH)₆PP] with excess Zn(O₂CCH₃)₂2H₂O for 1 hour. Methanol wasevaporated to dryness and the residue was dissolved in ethylacetate,washed with water, and the organic layer passed through anhyd. Na₂SO₄.The concentrated ethylacetate solution was passed through a silica gelcolumn and the first band was collected as the desired product. Theyield of the product was nearly quantitative. ¹H NMR of Zn(OH)₆PP inacetone-d₆ (ppm): 8.95-8.79(m, 8H, b-pyrrole H), 8.22(m, 2H, o-H5-Phenyl), 7.79(m, 3H, m,p-H 5-Phenyl), 7.75 and 7.65(2s, 6H, —OH),7.48(t, 3H,p-H hydroxyphenyl), 6.88(d, 6H, m-H hydroxyphenyl). Elementalanalysis, calcd. for ZnC₄₄H₂₈O₆N₄.H₂O: C=66.7, H=3.8, N=7.1 and Zn=8.3%.Found C=66.4, H=3.8, N=6.7 and Zn=8.2%. The compound showed molecularion peak at 774 (m/z calcd. for ZnC₄₄H₂₈O₆N₄=773) in FAB-MS.

[0101] Synthesis of5-phenyl-10,15,20-tris(2^(/),6^(/)-disilyloxyphenyl)-porphyrinatozinc(II),Zn(Si₆PP):

[0102] The hexasilylether porphyrin was synthesized by stirring a DMFsolution of5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxyphenyl)-porphyrinatozinc(II)(100 mg, 0.13 mmol) with t-butyldimethyl silylchloride (1.18 g, 7.8mmol) in presence of imidazole (1.2 g, 17.9 mmol) at 60° C. for 24 hunder nitrogen. After this period the reaction mixture was washed withwater and extracted in CHCl₃. The organic layer was dried over anhyd.Na₂SO₄. The crude reaction mixture was loaded on a short silica gelcolumn and eluted with mixture of CHCl₃/petether (1:1, v/v) to get ridof unreacted starting material and lower silylated products. The desiredcompound was further purified by running another silica gel columnchromatography using mixture of CHCl₃/petether (1:3, v/v) as eluant. Theyield of the product was 60% based on starting hydroxyporphyrin.

[0103]¹H NMR in chloroform-d (ppm): 8.94-8.82(m, 8H, b-pyrrole H),8.20(m, 2H, o-H 5-Phenyl), 7.74(m, 3H, m,p-H 5-Phenyl), 7.49(t, 3H, p-Hhydroxyphenyl), 6.91(t, 6H, m-H hydroxyphenyl), −0.02 and −0.34(2s, 54H,t-butyl H), −0.43, −0.78 and −1.01(3s, 36H, methyl H). Elementalanalysis, calcd. for ZnC₈₀H₁₁₂O₆N₄Si₆: C=65.8, H=7.7, N=3.8, Si=11.5 andZn=4.5%. Found C=65.5, H=7.7, N=3.8, Si=11.2 and Zn=4.4%. The lowresolution MALDI-TOF mass spectrum showed molecular ion peak at 1457(m/z calcd. for ZnC₈₀H₁₁₂O₆N₄Si₆=1458).

[0104] Synthesis of5,10,15-tris(2^(/),6^(/)-disilyoxyphenyl)-20-(2^(/)6^(/)-hydr-oxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II),[Zn(Si₇OHPP)], and5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphy-rinato-zinc(II),[Zn(Si₈PP)]:

[0105] The synthesis of precursor porphyrin5,10,15,20-tetrakis-(2^(/),6^(/)-dihydroxyphenyl)porphyrin and its Znderivative was accomplished as reported earlier. See Bhyrappa, P.;Vaijayanthimala, G.; Suslick, K. S. J. Am. Chem. Soc. 1999, 121, 262.The hepta-and octa-silylether porphyrins were synthesized by stirringDMF solution of5,10,15,20-tetrakis(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II)(100 mg, 0.12 mmol) with t-butyldimethyl silylchloride (1.45 g, 9.6mmol) in presence of imidazole (1.50 g, 22.1 mmol) at 60° C. for 24 hunder nitrogen. After usual work-up the mixture of crude products wereloaded on a silica gel column and eluted with mixture of CHCl₃/pet.ether (1:1, v/v) to remove unreacted starting material and lowersilylated products. The major product isolated from this column is amixture of hepta- and octa-silylated porphyrins. The mixture thusobtained was further purified by another silica gel columnchromatography using mixture of CHCl₃/pet. ether (1:3, v/v) as eluant.The first two bands were isolated as octa- and hepta-silyletherporphyrin at 45% and 30% yield, respectively. Both the compounds werecharacterized by UV-Visible, ¹H NMR and MALDI-TOF spectroscopictechniques. The homogeneity of the sample was verified by HPLC.

[0106] For Zn(Si₇OHPP), ¹H NMR in chloroform-d (ppm): 8.91(m, 8H,b-pyrrole H), 7.50(m, 4H, p-H), 7.01-6.81(m, 8H, m-H), 0.11 to−0.03(12s, 105H, t-butyl and methyl H). Elemental analysis, calcd. forZnC₈₆H₁₂₆O₈N₄Si₇: C=64.3, H=7.8, N=3.5, Si=12.3 and Zn=4.1%. FoundC=63.6, H=8.1, N=3.5, Si=12.1 and Zn=3.9%. The low resolution MALDI-TOFmass spectrum showed molecular ion peak at 1604 (m/z calcd. forZnC₈₆H₁₂₆O₈N₄Si₇=1604).

[0107] For Zn(Si₈PP), ¹H NMR in chloroform-d (ppm): 8.89(s,8H, b-pyrroleH), 7.49(t, 4H, p-H), 6.92(d,8H, m-H), 0.09(s, 72H, t-butyl H), −1.01(s,48H, methyl H). Elemental analysis, calcd. for ZnC₉₂H₁₄₀O₈N₄Si₈: C=64.2,H=8.1,N=3.3, Si=13.1 and Zn=3.8%. Found C=63.5, H =8.4, N=3.3, Si=12.8and Zn=4.0%. The low resolution MALDI-TOF mass spectrum showed molecularion peak at 1719 (m/z calcd. for ZnC₉₂H₁₄₀O₈N₄Si₈=1718).

[0108] Many modifications and variations may be made in the techniquesand structures described and illustrated herein without departing fromthe spirit and scope of the present invention. Accordingly, thetechniques and structures described and illustrated herein should beunderstood to be illustrative only and not limiting upon the scope ofthe present invention.

What is claimed is:
 1. An artificial nose comprising an array, the arraycomprising at least a first dye and a second dye in combination andhaving a distinct spectral response to an analyte wherein the first dyeor the second dye are porphyrins each having a periphery and wherein atleast the first porphyrin or the second porphyrin has a superstructurebonded to the respective periphery thereof.
 2. The artificial nose ofclaim 1 wherein the superstructure is from the group comprisingsiloxyl-substituted substituents and nonsiloxyl-substitutedsubstituents, including aryl substituents, alkyl substituents, andorganic, organometallic, and inorganic functional group substituents. 3.The artificial nose of claim 1 wherein the superstructure is shapeselective, polarity selective, inantio selective, regio selective,hydrogen bonding selective, or acid-base selective.
 4. The artificialnose of claim 1 wherein either the first porphyrin or the secondporphyrin is a siloxyl-substituted bis-pocket porphyrin.
 5. Theartificial nose of claim 4 wherein the siloxyl-substituted bis-pocketporphyrin is made in accordance with the synthesis shown in FIG.
 13. 6.The artificial nose of claim 4 wherein the siloxyl-substitutedbis-pocket porphyrin is from the group consisting of Zn(TPP),5,10,15,20-tetraphenylporphyrinatozinc(II); Zn[(OH)₆PP], 5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn[(OH)₈PP],5,10,15,20-tetrakis(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn(Si₆PP),5(phenyl)-10,15,20-trikis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II);Zn(Si₇OHPP),5,10,15-trikis(2^(/),6^(/)-disilyloxyphenyl)-20-(2^(/)-hydroxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II);and Zn(Si₈PP),5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II).7. The artificial nose of claim 1 wherein the array is part of a sensorplate.
 8. The artificial nose of claim 1 wherein the array is connectedto a wavelength sensitive light detecting device.
 9. The artificial noseof claim 8 wherein the wavelength sensitive light detecting devicecomprises a scanner.
 10. The artificial nose of claim 8 wherein thewavelength sensitive light detecting device comprises a charge-coupleddevice.
 11. The artificial nose of claim 1 wherein the array is aspatially resolved collection of dyes.
 12. The artificial nose of claim1 wherein the array is a spatially resolved combinatorial family ofdyes.
 13. A method of detecting an analyte comprising the steps offorming an array of at least a first dye and a second dye incombination, subjecting the array to an analyte, and inspecting thefirst dye and the second dye for a spectral response corresponding tothe analyte wherein the first dye or the second dye are porphyrins eachhaving a periphery and wherein at least the first porphyrin or thesecond porphyrin has a superstructure bonded to the respective peripherythereof.
 14. The method of claim 13 wherein the superstructure is fromthe group comprising siloxyl-substituted substituents andnonsiloxyl-substituted substituents, including aryl substituents, alkylsubstituents, and organic, organometallic, and inorganic functionalgroup substituents.
 15. The method of claim 13 wherein thesuperstructure is shape selective, polarity selective, inantioselective, regio selective, hydrogen bonding selective, or acid-baseselective.
 16. The method of claim 13 wherein either the first porphyrinor the second porphyrin is a siloxyl-substituted bis-pocket porphyrin.17. The method of claim 16 wherein the siloxyl-substituted bis-pocketporphyrin is made in accordance with the synthesis shown in FIG.
 13. 18.The method of claim 13 wherein the siloxyl-substituted bis-pocketporphyrin is from the group consisting of Zn(TPP),5,10,15,20-tetraphenylporphyrinatozinc(II); Zn[(OH)₆PP],5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn[(OH)₈PP],5,10,15,20-tetrakis(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn(Si₆PP),5(phenyl)-10,15,20-trikis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II);Zn(Si₇OHPP),5,10,15-trikis(2^(/),6^(/)-disilyloxyphenyl)-20-(2^(/)-hydroxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II);and Zn(Si₈PP),5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II).19. The method of claim 13 having the step of placing the array on asensor plate.
 20. The method of claim 13 having the step of connectingthe array to a visual display or detection device.
 21. The method ofclaim 20 wherein the wavelength sensitive light detecting devicecomprises a scanner.
 22. The method of claim 20 wherein the wavelengthsensitive light detecting device comprises a charge-coupled device. 23.The method of claim 13 wherein the array is a spatially resolvedcollection of dyes.
 24. The method of claim 13 wherein the array is aspatially resolved combinatorial family of dyes.
 25. The method of claim13 having the further step of comparing the spectral response with acatalog of analyte spectral responses to identify the analyte.
 26. Anartificial tongue comprising an array, the array comprising at least afirst dye and a second dye in combination and having a distinct spectralresponse to an analyte in solution or a liquid analyte, or an analyte ina solid or a solid analyte, wherein the first dye or the second dye areporphyrins each having a periphery and wherein at least the firstporphyrin or the second porphyrin has a superstructure bonded to therespective periphery thereof.
 27. The artificial tongue of claim 26wherein the superstructure is from the group comprisingsiloxyl-substituted substituents and nonsiloxyl-substitutedsubstituents, including aryl substituents, alkyl substituents, andorganic, organometallic, and inorganic functional group substituents.28. The artificial tongue of claim 26 wherein the superstructure isshape selective, polarity selective, inantio selective, regio selective,hydrogen bonding selective, or acid-base selective.
 29. The artificialtongue of claim 26 wherein either the first porphyrin or the secondporphyrin is a siloxyl-substituted bis-pocket porphyrin.
 30. Theartificial tongue of claim 29 wherein the siloxyl-substituted bis-pocketporphyrin is made in accordance with the synthesis shown in FIG.
 13. 31.The artificial tongue of claim 29 wherein the siloxyl-substitutedbis-pocket porphyrin is from the group consisting of Zn(TPP),5,10,15,20-tetraphenylporphyrinatozinc(II); Zn[(OH)₆PP],5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn[(OH)₈PP],5,10,15,20-tetrakis(2^(/),6^(/)-dihydroxyphenyl)porphyrinatozinc(II);Zn(Si₆PP),5(phenyl)-10,15,20-trikis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II);Zn(Si₇OHPP),5,10,15-trikis(2^(/),6^(/)-disilyloxyphenyl)-20-(2^(/)-hydroxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II);and Zn(Si₈PP),5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphyrinatozinc(II).32. The artificial tongue of claim 26 wherein the array is part of asensor plate.
 33. The artificial tongue of claim 26 wherein the array isconnected to a wavelength sensitive light detecting device.
 34. Theartificial tongue of claim 33 wherein the wavelength sensitive lightdetecting device comprises a scanner.
 35. The artificial tongue of claim33 wherein the wavelength sensitive light detecting device comprises acharge-coupled device.
 36. The artificial tongue of claim 26 wherein thearray is a spatially resolved collection of dyes.
 37. The artificialtongue of claim 26 wherein the array is a spatially resolvedcombinatorial family of dyes.
 38. A porphyrin having the chemicalformula Zn[(OH)₆PP],5-phenyl-10,15,20-tris(2^(/),6^(/)-dihydroxy-phenyl)-porphyrinatozinc(II).39. A porphyrin having the chemical formula Zn(Si₆PP),5-phenyl-10,15,20-tris(2^(/),6^(/)-disilyloxyphenyl)-porphyrinatozinc(II).40. A porphyrin having the chemical formula Zn(Si₇OHPP),5,10,15-tris(2^(/),6^(/)-disilyoxyphenyl)-20-(2^(/)6^(/)-hydr-oxy-6^(/)-silyloxyphenyl)porphyrinatozinc(II).41. A porphyrin having the chemical formula Zn(Si₈PP),5,10,15,20-tetrakis(2^(/),6^(/)-disilyloxyphenyl)porphy-rinato-zinc(II).